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"Trailer hitching" problem

I have '87 BMW 316 (1600 cc) - dual powered (LPG + petrol) carburetor engine.

My problem is at ~2000 +/- 250 rpm. The car sort of bogs down at short intervals. Someone described that as trailer hitching (with loose hitch).

At lower or higher rpm it's OK.

It's like that with both stock ignition system and with the MJLJ (electronic programmable ignition system).

I changed carburetor (for another reason), I also tried without carburetor (LPG only), and it is always there.

Maybe unrelated, but engine shakes a little at idle.

What can cause this?

Reply to
Yvan
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No end of things. Start with the cheap ones, get a dial guage & check the actual cam timing, then a lamda MAP, you might have the wrong progression drilings on the carb.

Reply to
Duncan Wood

Nedavno Duncan Wood napisa:

As I wrote problem exists both with (correctly tuned) original distributor ignition system, and the one I fitted (Ford EDIS based) programmable distributorles ignition system.

I tried advancing / retarding ignition around 2000 rpm, and it did not help.

As a part of the new ignition system I have MAP sensor and I can log MAP as I drive. What do I look for? Whit is lamda? Do you mean lambda sensor? I do not have it.

And I also changed carburetor, and even tested without it (LPG only). So perhaps I can rule out progression drilings (and I have the original, factory fitted carburetor too).

Reply to
Yvan

Check the cam is timed up right (not the ignition).

Reply to
Duncan Wood

Nedavno Duncan Wood napisa:

And how do I do that? And wouldn't that create problems at any rpm, not just ~2000?

Reply to
Yvan

Set a dial guage on top of the engine & measure when the valves open. Then check it with the spec. It will reduce power at other rpm but not necessarily by very much. Does a little extra advance on the ignition have any effect on the stutter?

Reply to
Duncan Wood

Nedavno Duncan Wood napisa:

Only now I realized that you wrote "check the actual cam timing". I missed word CAM, and that's why I was confused :-)

I do not think that this can be a problem. I have this car from new, and it has chain not timing belt. It was never touched, and car only has 35000 miles on the clock.

I tried to advance / retard timing at ~2000 rpm - nothing.

Reply to
Yvan

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